This invention lies in the field of elastomer seal ring means. More particularly it concerns a seal ring adapted to seal a contact surface between two plates, and simultaneously to seal between a cylindrical opening bored through the plates perpendicular to the contact surface and a piston inserted into the bored opening.
In the prior art it has been customary to provide a recess in the wall of the bored opening at the contact plane between the two plates and to insert a toroidal ring, or O-ring, into the recess to seal between the plates and the piston.
As the piston moves throughout its full stroke it may move beyond the position of the seal ring and some means must be provided to restrain the seal ring in its recess so that as the piston moves back to the position of the seal ring the ring will be within the recess.